D131 — --package-tunnels under dense packages

Decision

--package-tunnels: stub, via and back-layer run between two perimeter pins of one net on a dense package, placed before the lanes (doc 05 §52)

Context

In every best state of the EtherCAT study the last open connection was the core rail's pin 38, cut off from its trunk under the package; the designer's solution is a tunnel (review item 5)

Consequences and results

Off by default; every piece passes the exact check and nothing is placed unless the whole tunnel does; costs connections at the loose first-round rules, to be judged in the closure loop